Greg, those Atlanta cards were from a set that my brother (Rhys) and I purchased several years ago off an ebay seller after his item didn't reach the minimum bid he was looking for. I remember we found record of another set that was in a library/museum collection in the Atlanta area but other than that they are the only examples we had ever seen. We sold the set to Terry Sr. maybe 5 years ago and he has had them since but was only looking to sell as a complete set until this show (assuming ou only bought the one single).
I can't help but think they are related somehow to the 1909 Atlanta oversized postcards that are among the rarest of the early PC's sets, just due to the similarity in the way they look. There are only (2) known subjects in the PC set: Roy Castleton, and Dick Bayless. To my knowledge each postcard is either unique or perhaps there is a second copy known of each but I haven't seen them. Here is the Castleton that I currently own...
Regardless, it is a great piece and I wouldn't mind owning one again.
-Rhett